Lipid oxidation and production of off-odor in irradiated meat

Emulsion-type raw and cooked pork sausage with different fat content or fatty acids was prepared to determine the effect of irradiation on lipid and cholesterol oxidation, color changes, and volatile production during storage. Lipid oxidation increased with the increase of fat content or irradiation dose in both raw and cooked pork products. Irradiated batters had higher cholesterol oxide content than non-irradiated, and the major cholesterol oxides formed in raw irradiated pork batters were 7alpha- and 7beta-hydroxycholesterol. Hunter a- and b-values of both raw and cooked pork products in aerobic packaging decreased with irradiation regardless of fat content. In vacuum packaging, however, irradiated cooked pork sausage had higher Hunter a-values than nonirradiated. Irradiation significantly increased the amount of 1-heptene, 1-nonene, and total volatile compounds in raw and cooked pork sausage. The amounts of 1-heptene and 1-nonene were not associated with TBARS values of pork sausage but were closely related to irradiation dose. In both irradiated and nonirradiated pork sausage, aerobic packaging produced more volatile compounds during storage than did vacuum packaging. The production of aldehydes, ketones, and alcohols in aerobic-packaged pork sausage were not influenced by irradiation at O-day storage. However, irradiation accelerated lipid oxidation and increased the amounts of aldehydes, ketones, and alcohols during storage. The TBARS of aerobic- or vacuum-packed sausage prepared with lard were higher (p \u3c 0.05) than the sausage prepared with flaxseed oil likely a result of the high tocopherol content in flaxseed oil;To investigate the distinction between volatile compounds related to oxidized flavor and irradiation odor, and to understand the mechanisms of off-odor production in irradiated meat on a chemical basis, oil emulsions containing amino acids or proteins were analyzed. The increase of aldehydes (e.g. hexanal, heptanal, octanal, and nonanal, p \u3c 0.05) in the oil emulsion after irradiation indicated that irradiation accelerated lipid oxidation of the oil emulsion model system containing amino acids, glutathione, bovine serum albumin, gelatin, or myofibrillar proteins. Irradiation also produced new volatile compounds from amino acids (e.g., leucine, valine, isoleucine, phenylalanine, methionine, and cysteine) via radiolytic degradation. These radiolytic compounds along with lipid oxidation by-products may be the major sources of off-odor from irradiated meat

Lipid Oxidation, Volatiles, and Off-Odor Production of Aerobic-Packaged Pork Patties Irradiated and Stored in Refrigerated or Frozen Conditions

Pork loins were ground twice through a 9-mm plate and patties (approximately 80 g each) were made. Patties were individually packaged in oxygenpermeable polyethylene zipper bags, stored overnight either at 4 or -40° C, and irradiated the next day at 0, 1.5, 3.0, or 4.5 kGy absorbed dose for refrigerated patties, and at 0, 2.5, 5.0, or 7.5 kGy for frozen ones. Samples were analyzed for lipid oxidation, volatile production, and off-odor. Refrigerated samples were analyzed at 0, 1 and 2 weeks of storage at 4°C, and frozen ones were analyzed after 0, 1.5 and 3 months of storage at -40°C. 2-Thiobarbituric acid reactive substances (TBARS) of refrigerated pork patties increased with storage time. TBARS of pork patties increased as irradiation dose increase at 0 day, but the irradiationdose effect disappeared after 1-week of storage at 4°C. Irradiated pork patties produced significant irradiation odor at day 0, but disappeared following storage. Nonirradiated samples were preferred to the irradiated ones at beginning (day 0), but the preference disappeared after 1-week of storage. With frozen storage, TBARS values of irradiated pork patties were not increased by storage. However, patties irradiated at higher dose (7.5 kGy) had higher TBARS value than the nonirradiated or irradiated patties at lower levels. Nonirradiated patties had higher preference scores than the irradiated ones and the difference lasted for 1.5 month in frozen storage. Sulfur-containing compounds such as 2,3- dimethyldisulfide were responsible for most of the irradiation off-odor, but volatilized quickly under aerobic conditions. However, aerobic packaging was not recommended for irradiated meat because of oxidative changes in pork patties during storage

Quality Characteristics of Vacuum-Packaged Pork Patties Irradiated and Stored in Refrigerated or Frozen Conditions

Pork loins were ground twice through a 9-mm plate and patties (approximately 80 g each) were made. Patties were individually vacuum-packaged in oxygen impermeable plastic bags and stored either in a cooler (4°C) or a freezer (-40°C). Refrigerated patties were irradiated 0, 1.5, 3.0, or 4.5 kGy and stored at 4°C for 2 weeks, and frozen ones were irradiated at 0, 2.5, 5.0, or 7.5 kGy and stored at - 40°C for 3 months. Samples were analyzed for lipid oxidation, volatile production, and off-odor during refrigerated or frozen storage. The 2-thiobarbituric acid reactive substances (TABRS) values of both refrigerated and frozen patties were not changed during storage. Irradiation dose had no effect on the TBARS of refrigerated patties, but patties irradiated at 7.5 kGy had higher TBARS value than the nonirradiated control. With refrigerated storage, panels could detect irradiation odor at day 0, but could not detect after 1 week of storage at 4°C. With frozen storage, however, irradiation odor was detected even after 3 months of storage. No difference in odor preference was found between irradiated and nonirradiated samples. Vacuum packaging was better than aerobic packaging for irradiation and subsequent storage of meat because it could minimize oxidative changes in patties during storage and produced minimal amount of volatile compounds responsible for irradiation odor

Analysis of Volatile Components and Sensory Characteristics of Irradiated Raw Pork

Longissimus dorsi muscle strips of pig packaged either aerobically or under vacuum were irradiated at 0, 5, or 10 kGy and stored at 4°C for 5 days. Lipid oxidation, the amount and identity of volatile components, and sensory characteristics of raw pork strips were determined at 0 and 5 days of storage. Irradiated muscle strips produced more 2- thiobarbituric acid reactive substances (TBARS) than nonirradiated only in aerobic packaging during storage. Irradiation had no effect on the production of volatiles related to lipid oxidation, but produced a few sulfur-containing compounds not found in nonirradiated meat. This indicates that the major contributor of off-odor in irradiated meat is not lipid oxidation, but radiolytic breakdown of sulfurcontaining amino acids. Many of the irradiationdependent volatiles reduced to 50 to 25% levels during the 5-d storage under aerobic conditions. Irradiated muscle strips produced stronger irradiation odor than nonirradiated, but no irradiation dose or storage effect was found. Irradiation had no negative effect on the acceptance of meat, and approximately 70% of sensory panels characterized irradiation odor as barbecued-cornlike odor

Flavour Chemistry of Chicken Meat: A Review

Flavour comprises mainly of taste and aroma and is involved in consumers’ meat-buying behavior and preferences. Chicken meat flavour is supposed to be affected by a number of ante- and post-mortem factors, including breed, diet, post-mortem ageing, method of cooking, etc. Additionally, chicken meat is more susceptible to quality deterioration mainly due to lipid oxidation with resulting off-flavours. Therefore, the intent of this paper is to highlight the mechanisms and chemical compounds responsible for chicken meat flavour and off-flavour development to help producers in producing the most flavourful and consistent product possible. Chicken meat flavour is thermally derived and the Maillard reaction, thermal degradation of lipids, and interaction between these 2 reactions are mainly responsible for the generation of flavour and aroma compounds. The reaction of cysteine and sugar can lead to characteristic meat flavour specially for chicken and pork. Volatile compounds including 2-methyl-3-furanthiol, 2-furfurylthiol, methionol, 2,4,5-trimethyl-thiazole, nonanol, 2-trans-nonenal, and other compounds have been identified as important for the flavour of chicken. However 2-methyl-3-furanthiol is considered as the most vital chemical compound for chicken flavour development. In addition, a large number of heterocyclic compounds are formed when higher temperature and low moisture conditions are used during certain cooking methods of chicken meat such as roasting, grilling, frying or pressure cooking compared to boiled chicken meat. Major volatile compounds responsible for fried chicken are 3,5-dimethyl-1,2,4-trithiolanes, 2,4,6-trimethylperhydro-1,3,5-dithiazines, 3,5-diisobutyl-1,2,4-trithiolane, 3-methyl-5-butyl-1,2,4-trithiolane, 3-methyl-5-pentyl-1,2,4-trithiolane, 2,4-decadienal and trans-4,5-epoxy-trans-2-decenal. Alkylpyrazines were reported in the flavours of fried chicken and roasted chicken but not in chicken broth. The main reason for flavour deterioration and formation of undesirable “warmed over flavour” in chicken meat products are supposed to be the lack of α-tocopherol in chicken meat

Factors Affecting Cooked Chicken Meat Flavour: A Review

Flavour, one of the most important factors affecting consumers’ meat-buying behaviour and preferences, comprises mainly of taste and aroma. The cooked meat flavour, that is important from the producer and consumer point of view, is affected by several pre- and post-slaughter factors, including breed, diet, post-mortem ageing, and method of cooking. Moreover, chicken meat is prone to the development of off-flavours through lipid oxidation, which reduce the quality of the chicken meat. The aim of this review is to discuss the main factors affecting cooked chicken meat flavour which helps producers and consumers to produce the most flavoured and consistent product possible. Cooked chicken meat flavour is thermally derived via the Maillard reaction, the degradation of lipids, and interaction between these two reactions. Factors affecting the flavour of cooked chicken meat were identified as breed/strain of the chicken, diet of the bird, presence of free amino acids and nucleotides, irradiation, high pressure treatment, cooking, antioxidants, pH, and ageing

Irradiation of Shell Egg on the Physicochemical and Functional Properties of Liquid Egg White

The effect of irradiation of shell eggs on the physiochemical and functional properties, and color and textural parameters of liquid egg white during storage were determined. Shell eggs were irradiated at 0, 2.5, 5, or 10 kGy using a linear accelerator. Viscosity, pH, turbidity, foaming properties, color, and volatile profile of liquid egg white, and color and texture properties of cooked egg white were determined at 0, 7, and 14 days of storage. Irradiation increased the turbidity but decreased viscosity of liquid egg white. Foaming capacity and foam stability were not affected by irradiation at lower dose (2.5 kGy), but were deteriorated at higher doses (≥ 5.0 kGy) of irradiation. Sulfur-containing volatiles were generated by irradiation and their amounts increased as the irradiation dose increased. However, the sulfur volatiles disappeared during storage under aerobic conditions. Lightness (L* value) and yellowness (b* value) decreased, but greenness (-a * value) increased in cooked egg white in irradiation dose-dependent manners. All textural parameters (hardness, adhesiveness, cohesiveness, chewiness, and resilience) of cooked egg white increased as the irradiation dose increased, but those changes were marginal. Our results indicated that irradiation of shell egg at lower doses (up to 2.5 kGy) had little negative impact on the physiochemical and functional properties of liquid egg white, but can improve the efficiency of egg processing due to its viscosity-lowering effect. Therefore, irradiation of shell eggs at the lower doses has high potential to be used by egg processing industry to improve the safety of liquid egg without compensating its quality

Separation of Phosvitin from Egg Yolk without Using Organic Solvents

The objective of this study was to develop a new method to separate phosvitin from egg yolk without using organic solvents. Phosvitin was extracted from yolk granules using 10% NaCl or 10% (NH4)2SO4 (final concentration) and then treated with heat to precipitate the lipoproteins from the extracted solution. The optimal pH for the phosvitin extraction from yolk granules was determined, and the iron-binding ability of the extracted phosvitin (final product) was tested. Adding 10% (NH4)2SO4 disrupted the granules, and the subsequent thermal treatment at 90°C for 1 h precipitated low density and high density lipoproteins, which enabled separation of phosvitin by centrifugation. The phosvitin concentration in the extract was significantly higher when the pH of the solution was adjusted to pH ≥9. The purity and recovery rate of phosvitin at the end of the separation process were approximately 78% and 56%, respectively. The separated phosvitin was confirmed to have ferrous and ferric iron binding ability. The advantages of this new method compared with the traditional methods include no organic solvents and high-priced equipment are needed for the separation. Also, this method is more environment and consumer friendly than that of the traditional methods

Monitoring the formation of cholesterol oxidation products in model systems using response surface methodology

BACKGROUND: Cholesterol oxidation products (COPs) are produced during thermal processing of animal origin foods and are considered to have negative health impacts. The model systems are helpful to understand the impact of various factors on oxidation changes in foods during cooking process. METHODS: The study presented herein investigates the effects of pH, presence of unsaturated fatty acids, and heat on the formation of cholesterol oxidation products (COPs). Two model systems were designed to investigate the formation of cholesterol oxidation products in different lipid environments. The cholesterol oxides produced were quantified using gas chromatography. RESULTS: The level of cholesterol oxidation products decreased significantly at higher pH (above 5.8) and shorter heating time (3 h). The presence of unsaturated fatty acids (linoleic and oleic acids) significantly increased the amount of COPs under low-temperature heating conditions (100 °C and 1 h) but did not affect the production of COPs at higher temperature (150 °C). Increasing the temperature to 200 °C significantly increased the amount of COPs during the first hour of heating and this amount decreased upon further heating. The most frequently observed COPs in samples were α-epoxide, 20α-hydroxycholesterol, and 25-hydroxycholesterol. CONCLUSIONS: In conclusion, pH below 5.8, presence of unsaturated fatty acid, and high cooking temperature (>150 °C) leads to increased production of cholesterol oxidation products

Evaluation of the physicochemical, metabolomic, and sensory characteristics of Chikso and Hanwoo beef during wet aging

Objective This study aimed to evaluate the physicochemical, metabolomic, and sensory qualities of Chikso and Hanwoo beef during 28 days of wet aging. Methods Rump and loins from Hanwoo and Chikso were obtained and wet-aged for 28 days at 4°C. The samples were collected at 7-day interval (n = 3 for each period). Physicochemical qualities including pH, meat color, shear force value, and myofibrillar fragmentation index, metabolomic profiles, and sensory attributes (volatile organic compounds and relative taste intensities) were measured. Results Chikso showed a significantly higher shear force value than Hanwoo on day 0; however, no differences between breeds were found after day 14, regardless of the cuts. Overall, Chikso had more abundant metabolites than Hanwoo, especially L-carnitine and tyrosine. Among the volatiles, the ketone ratio was higher in the Chikso rump than the Hanwoo rump; however, Chikso had fewer alcohols and aldehydes than Hanwoo. Chikso rump showed higher taste intensities than the Hanwoo rump on day 0, and sourness decreased in Chikso, but increased in the Hanwoo rump on day 14. Wet aging for 14 days intensified the taste of Chikso loin but reduced the umami intensity of Hanwoo loin. Conclusion Chikso had different metabolomic and sensory characteristics compared to Hanwoo cattle, and 14 days of wet aging could improve its tenderness and flavor traits